1. Field of the Invention
The present invention relates to a spray gun with an automatic valve opening control means which enables remote and stepless control of a paint spraying operation in response to an external signal.
2. Description of the Related Art
A typical conventional spray gun which is controlled by external signals has heretofore been arranged such that a necessary number of control valves are disposed in each of the paint and air systems in the spray gun, and the valves are set in different conditions in advance and are opened and closed as well as being selectively combined with each other in response to external signals, thereby allowing the amount of paint sprayed and the spray pattern width to be controlled such as to meet particular spraying conditions such as the configuration, size, etc. of various kinds of object (see, e.g., the specification of Japanese Utility model Public disclosure No. 48769/1984 which was previously filed by the applicant of this application). This type of conventional spray gun suffers, however, from the following problems. Since the range of control of the amount of paint sprayed and the spray pattern width is limited by the number of control valves provided, the range of use of the spray gun is inconveniently limited. In addition, since each control valve has an arrangement similar to that of the spray gun itself (see the specifictation of Japanese Utility Model Public Disclosure No. 48764/1984 filed by the same applicant of this invention), the cost of the spray gun as a whole is unfavorably high.
Further, the above-described conventional spray gun involves certain difficulties in terms of speedily and accurately transmitting to atomizing means a flow rate determined by a control valve which is remote from the atomizing means due to possible residual pressure of paint or compressed air, which means that the response speed and sensitivity are unsatisfactory.